This invention relates generally to systems for determining a mean frequency of a plurality of signal sequences, and more particularly, to a system for determining a median frequency of three periodic digital pulse sequences.
Electronic systems for selecting a median frequency from a plurality of signals find application in the fields of measurement, control, and regulation engineering. Such systems, however, have heretofore required complex processing equipment which converts the original data in the form of periodic signal sequences into equivalent intermediate variables and parameters. Further processing is then required to produce a signal responsive to the desired median frequency. There is a need, therefore, for a system which produces the desired median frequency signal directly from the plural original periodic signal sequences. Such a system would be particularly useful in fail-safe monitoring equipment which transmits measurement information over a plurality of redundant channels so as to achieve a desired degree of system reliability.
It is a further problem with known systems that noise and interference signals may undesirably couple with one or more of the redundant measurement channels. Such undesirable coupling may be inductive in nature and result in the transmission of erroneous measurement information. There is, therefore, a need for systems which can distinguish measurement channels which have been subjected to such undesirable signal coupling, from undisturbed channels.
It is, therefore, an object of this invention to provide a multiple channel measuring system which simply and economically determines a median system frequency.
It is a further object of this invention to provide an improved multiple channel measurement system which can distinguish between disturbed and undisturbed channels.